Vulcanizable rubber compositions

ABSTRACT

Vulcanizable rubber compositions comprising a sulfur vulcanizable rubber, sulfur, a thiazole sulfenamide accelerator, a morpholinothio amide compound, and optionally a benzothiazole or thiuram accelerator exhibit good scorch safety and yield vulcanizes having excellent original and heat aged properties.

United States Patent [:91

Son

[ 1 Oct. 7, 1975 1 VULCANIZABLE RUBBER COMPOSITIONS [75] Inventor:

[73] Assignee: The B. F. Goodrich Company, Akron, Ohio [22 Filed: June 6, 1973 211 App1,N0.:367,642

Pyong-Nae Son, Akron, Ohio [56] References Cited UNITED STATES PATENTS 3,546,185 12/1970 Coran et a1. 260/795 B 3,562 225 2/1971 Coran et al. 260/786 3,573,262 3/1971 Morche et alv r i 1 260/795 B 3,671,503 6/1972 Schubart et al. 260/795 B 3,770,758 ll/1973 Kerwood w 4. 260/795 8 3,780,001 12/1973 Son 1 1 1 1 i 260/795 A 3,838 14 9/1974 Lawrence 1. 260/795 13 Primary Examiner-Ronald W. Griffin Attorney, Agent, or Firm-Alan A. Csontos [5 7 1 ABSTRACT Vulcanizable rubber compositions comprising a sulfur vulcanizable rubber, sulfur, a thiazole sulfenamidc accelerator, a morpholinothio amide compound, and optionally a benzothiazole or thiuram accelerator exhibit good scorch safety and yield vulcanizates having excellent original and heat aged properties.

7 Claims, N0 Drawings VULCANIZABLE RUBBER COMPOSITIONS BACKGROUND OF THE INVENTION It is known in the art that the use of various specific sulfur-accelerator combinations yield rubber vulanizates having particularly desirable properties. One instance of this is the use of sulfur and 2-benzothiazole 4-morpholino disulfide (BMD) to yield vulcanizatcs having excellent thermal aged properties. Such vulcanizates would be extremely useful as gaskets, automotive hose and tires, and other products where good retention of properties on heat aging is needed. Unfortu nately, the sulfur-BMD cure system is very fast acting, and yields quite scorchy rubber compositions having little processing safety. This prevents the use of such a cure system in operations where the vulcanizable rubber compositions must be handled and processed for extended periods at elevated temperatures, as in tire manufacturing. The use of known cure retarders provides only a marginal increase in scorch safety when employed with the sulfur-BMD cure system.

SUMMARY OF THE INVENTION vulcanizable rubber compositions comprising (l) a sulfur vulcanizable rubber, (2) sulfur, (3) a thiazole sulfenamidc accelerator, (4) a morpholinothioamide compound selected from the group consisting of morpholinothiooxamides of the formula wherein R is selected from the group consisting of hydrogen, alkyl radicals containing 1 to 24 carbon atoms, an aryl, alkaryl, or aralkyl radical containing 6 to l8 carbon atoms, a cycloalkyl radical containing 3 to 8 carbon atoms in the ring, and the group and a morpholinothio cyclic hydrocarbon of the formula wherein R is hydrogen or an alkyl radical containing 1 to 4 carbon atoms and Y and Y' are the same as R', or Y and Y together with the common carbon atoms on the HC ring form a cyclic hydrocarbon ring or a cyclic imide ring, and optionally a benzothiazole or thi uram accelerator exhibit good scorch safety on curing and yield vulcanizates having excellent original and heat aged properties. Vulcanizate properties are com parable with those obtained using a sulfur-BMD cure system.

DETAILED DESCRIPTION The vulcanizable rubber compositions comprise l a sulfur vulcanizable rubber, (2) sulfur, (3) a thiazole sulfenamide accelerator, (4) a morpholinothioamide compound, and optionally (5) a benzothiazole or thiuram accelerator. The rather complex system represents a unique balance of cure factors which yields good scorch safety at processing temperatures and vulcanizates having excellent original and heat aged proper ties. The compositions are particularly useful to prepare articles that require relatively long processing and shaping operations and/or are subject to thermal aging conditions. Such articles would be tires, belting, hose, gasketing, seals, and the like.

The sulfur vulcanizable rubber contains from about 0.5 percent to about 50 percent by weight of olefinic C=C unsaturation based upon the weight of the polymer. The olefinic groups can be in the polymer main chain (backbone) or in pendant (side-chain) groups, or both. Examples of such polymers are high unsaturation rubbers such as natural rubber, cispolyisoprene, cis-polybutadicne (CB), emulsion polybutadiene, butadiene-acrylonitrile (NBR) rubbers, isoprene-acrylonitrile rubbers, polychloroprene, polypentenamer rubbers, butadiene-styrene rubbers (SBR isoprene-styrene rubbers, and the like; and low unsaturation polymers such as isoprene-isobutylene (butyl) rubbers, copolymers of conjugated dienes with lower alkyl and alkoxy acrylates like ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and the like; polyether, terpolymers containing up to 20 percent by weight of glycidyl acrylate, allyl glycidyl ether, and the like; and ethylene-propylenediene polymers (EPDM) containing from about 0.5 percent to about 20 percent by weight of a diene monomer where the diene can be conjugated as in butadiene, l,3-pentadiene, and the like; nonconjugated as in 1,4-pentadiene, l,4-hexadiene, and the like; cyclic dienes as in cyclopentadiene, dicyclopentadiene, and the like; an alkenyl norbornene such as 5-ethylidene-2-norbornene, 2-isopropenyl-5- norbornene, and the like; and others such as 3-ethylbicyclonondiene, methyl tetrahydroindene, and 3-methyl-tricyclo-( 5,2, l ,0 ")-3,8-decadiene.

Although the disclosure is directed to the use of a sulfur vulcanizable rubber, blends of two or more sulfur vulcanizable rubbers are readily employed. For example, the rubber can be a polymer blend of styrenebutadiene rubber and polybutadiene rubber, or a terblend of natural or polyisoprene rubber with polybutadiene and poly(butadicnestyrene)rubber.

The second ingredient in the composition is sulfur. The level employed ranges from about 0.1 part to 0.8 part by weight per parts by weight of the sulfur vulcanizable rubber. More preferredly, the level of sulfur is from about 0.2 to aobut 0.6 part by weight. Excellent results are obtained when the sulfur is used at about 0.5 part by weight per l00 parts of rubber. Use of the sulfur is necessary to achieve the high state of cure and good fatigue life of the composition. However, use of levels of sulfur significantly higher than those designated results in inferior heat aged properties.

The third ingredient is a thiazole sulfenamide compound of the formula T-S-A wherein A is selected from the group consisting of i wherein R and R are hydrogen, alkyl radicals containing 1 to 24 carbon atoms, an aryl radical, alkaryl radical or aralkyl radical containing 6 to l8 carbon atoms, a cycloalkyl radical containing 3 to 8 carbon atoms in the ring, and R is hydrogen or an alkyl radical containing l to 4 carbon atoms and y is 2 to 7; and T is a thiazole ring and especially a benzothiazole ring. The alkyl radicals can be linear or branched and can contain primary, secondary and/or tertiary carbon atom configurations. The aryl, alkaryl, aralkyl, cycloalkyl and thiazole radicals can further be substituted with alkyl radicals containing l to 8 carbon atoms.

Examples of the thiazole sulfenamide compounds are N,N-dimethyl-2-benzothiazylsulfenamide, N,N,- diisopropyl-2-( 4,5-dimethylthiazyl )sulfenamide, N- methylN-cyclohcxyl-2-(4,5-dimethylthiazylsulfenamide), N,N-diisopropyl-2-benzothiazylsulfenamide, N- ,N-diethyl-2-benzothiazylsulfenamide, N-methyl-N- benzyl-2-benzothiazylsulfenamide, N,N-di(tert-butyl)- 2-benzothiazylsulfenamide, N,N-dicyclohexyl-Z-bcnzothiazylsulfcnamide, N-pentamethylene-2benzothiazylsulfenamide, N-oxydiethylcne-2-benzothiazylsulfenamide, N-( 2,6-dimethyl )-oxydiethylene-2-benzothiazylsulfenamide, N,N-dimethyl-2-(4,6-dimethylbenzothiaZyUsulfenamide, and the like.

More preferredly, the thiazole sulfenamide is a henzothiazole sulfenamide of the formula where T, is a benzothiazole ring which can be substituted with l to 4 carbon atom alkyl groups and A is selected from the group consisting of where R',, and R',, are alkyl radicals containing 1 to about [8 carbon atoms or a phenyl or cyclohexyl radical. Examples of the more preferred compounds are N- ,N-diethyl-Z-benzothiazylsulfenamide, N,N- diisopropyl-2-benzothiazylsulfenamide, N,N-dioctyl-2- benzothiazylsulfenamide, N,N-dioctadecyl-2-benzo thiazylsulfenamide, N,N-dicyclohexyl-2-benzothia1ylsulfenamide, N,N-diphenyl-2-benzothiazylsulfenamide, N-oxydiethylene-Z-benzothiazylsulfenamide, and the like. Excellent results are obtained when employing N- oxydiethylene-2-benzothiazylsulfenamide.

The thiazole sulfenamide accelerator is used in a level from about 1 part to about parts by weight, and often from about 2 parts to 4 parts by weight per l()0 parts by weight of rubber. The thiazolesulfenamide accelerator is necessary to achieve the high state of cure.

The last necessary ingredient is a morpholinothioamide compound. The compound contains the structure ONSlL C where R is defined the same as R, or is a group. Designating the left hand portion of the mole cule as the N,N nitrogen positions and the right hand side as the N, N positions, examples of the compounds are: N-morpholinothio oxamide, (N,N'- dimorpholinothio) oxamidc, N-morpholinothio-N'N diethyl oxamide, N-morpholinothio-N'-phenyl oxamide, N,N-dibenzyl-N'-morpholinothio oxamidc, N morpholinothio-N-octyl oxamide, Nmorpholinothio- N-octadecyl oxamide, N-morpholinothio-N'- cyclohexyl oxamide, N-morpholinothio-N-methyl-N'- decyl oxamide, N-morpholinothio oxanilide, (N,N'- dimorpholinothio) oxanilide, and the like. lf the morpholinothio oxamidc contains two morpholinothio groups. preferably one group is located on each nitrogen atom', i.e., one morpholinothio group at the N position and one at the N position.

More preferredly, the morpholinothiooxamides have the formula where R is hydrogen, an alkyl radical containing 1 to about l2 carbon atoms, a phenyl radical, or a cyclohexyl radical. and R" is the same as R or a group.

Examples of the more preferred compounds are Nmorpholinothiooxamide. N.N-dimorpholinothiooxamide, N-morpholinothio-N'.N'-diisopropyl oxamide,

N-morpholinothio-N',N'-dicyclohexyl oxamide, N- morpholinothio-N',N'-dioctyl oxamide, N-methyl-N- morpholinothio-N ,N '-diphenyl ox amide N- morpholinothio oxanilide, N,N'-dimorpholinothio oxanilide, and the like. Excellent results are obtained when using N-morpholinothiooxamide or N-morpholinothiooxanilide.

The morpholinothioamide compounds also include morpholinothio derivatives of cyclic hydrocarbon imides. Examples of such imides are phthalimide, dihydrophthalimide, tetrahydrophthalimide, pyromellitic diimide, naphthalimides, and the like. The cyclic hydrocarbon can be further substituted with l to 4 carbon atom alkyl radicals. The morpholinothio cyclic hydrocarbon imides have a structure which can be represented by where R is hydrogen or I to 4 carbon atom alkyl radicals, and Y and Y are the same as R or Y and Y can form with the common carbon atoms on HC" a cyclic hydrocarbon ring that is alicyclic or aromatic in nature or can form another cyclic imide group. Furthermore, the ring HC cna be an aromatic or an alicyclic ring. Examples of these compounds are: when Y and Y are equal to R, N-morpholinothiophthalimide, N- morpholinothio-dihydrophthalimide. N- morpholinothio-tetrahydrophthalimide, N- morpholinothio-S-methylphthalimide, N-

morpholinothio-S,o-diethylphthalimide, and the like; when Y' and Y together with the common carbon atoms of HC form another cyclic imide group, N- morpholinothio pyromellitic diimide, N,N- di(morpholinothio)pyromellitic diimide, and the like; and when Y and Y together with the common carbon atoms in HC form a cyclic hydrocarbon structure, N- morpholinothio-2,3-naphthalimidc, N-morpholinothio- 1,8 -naphthalimide, N-morpholinothio-2,3,6,7- naphthaldiimide. and the like. Excellent results are obtained when R, y, and Y are hydrogen and the HC ring is aromatic or alicyclic as in N-morpholinothiophthalimide and N-morpholinothiotetrahydrophthalimide.

The morpholinothioamide compound is used in a range from about I to about 5 parts by weight, and more preferredly from about 1.2 parts to about 3 parts by weight based upon 100 parts by weight of rubber.

As an optional fifth ingredient, the compositions can contain either a benzothiazole accelerator or a thiuram accelerator.

The benzothiazole accelerator thiobenzothiazole of the formula is' a 2- wherein X is a member selected from the group consisting of hydrogen; l to 18 carbon atom alkyl; aryl; halo-, nitro-, anilinoand alkyl-substituted aryl', a benzothiazolethio radical; and a monoor divalent radical selected from the group ammonium, sodium, potassium, calcium, zinc, cadmium, copper and lead. When X is a divalent metal the second valence of the metal may be satisfied with an alkyl, aryl, substituted-aryl or preferably with a second Z-thiobenzothiazole radical. In this latter instance the compound will correspond to the structure S-Me-S wherein Me is the divalent metal, preferably zinc, cadmium or lead. Exemplary benzothiazole compounds include: Z-mercaptobenzothiazole, 2 -octylthiobenzothiazole, 2,2'-mercaptobenzothiazole disulfide, sodium 2-mercaptobenzothiazole, potassium Z-mercaptobenzothiazole, ammonium 2-mercaptobenzothiazole, zinc 2-mercaptobenzothiazole 2-( 2,4-dinitrophenylthio benzothiazole, and the like. Excellent results are obtained when Z-mercaptobenzothiazole or 2,2'-mercaptobenzothiazole disulfide is employed.

The level of Z-thiobenzothiazole accelerator used is from about 0.05 part to 0.5 part by weight based upon [00 parts by weight of the sulfur vulcanizable rubber. The use of this small level of 2-thiobenzothiazole accelerator yields higher original and aged stress-strain properties. If significantly higher levels of the benzothiazole accelerator are used than is taught herein scorch safety is seriously impaired.

The thiuram accelerator has the formula where z is l or 2 and A is defined as before and B is the same as A. The thiuram is used in levels from about 0.05 part to 1 part by weight based upon parts by weight of the rubber and more preferably from about 0.l part to about 0.5 part by weight. The use of thiuram accelerator yields higher original and aged stress-strain properties. Again, the use of levels significantly higher than those designated seriously imparis scorch safety. Examples of the thiuram sulfide compounds are tetramethylthiuram monosulfide, tetraethylthiuram monosulfide, tetrabutylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraoctylthiuram disulfide, tetradodecylthiuram disulfide, tetraoctadecylthiuram disulfide, tetrabenzylthiuram disulfide, tetracyclohexylthiuram disulfide, N,N,-dimethyl-N N'- dibenzylthiuram disulfide, N ,N-dimethyl-N ,N diphenylthiuram disulfide, N,N-diethyl-N ,N

didecylthiuram disulfide, N-pentamethylene-N,N- dimethylthiuram disulfide, N,N-diethyl-N'-hexamethylenethiuram disulfide, N,N'-dipentamethylenethiuram disulfide, N-oxydiethylene-N,N'-dimethylthiuram disulfide, and the like.

More preferredly, the thiuram has A and B groups which are groups, wherein R,.' and R,, are defined as before. Even more preferred thiurams are tetraalkylthiurams, examples of which include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram monosulfide, tetraethylthiuram disulfide, tctrabutylthiuram disulfide, tetrahexylthiuram disulfide, tetradecylthiuram monosulfide, and the like.

Many compounding ingredients may be used with the novel compositions. Such ingredients include activators such as zinc, calcium, and magnesium oxide, lead monoxide and dioxide, fatty acids such as stearic and lauric acid, and salts thereof such as cadmium, zinc and copper stearatc and lead oleate; fillers such as channel blacks, reinforcing blacks, and thermal blacks, calcium and magnesium carbonate, calcium and barium sulfates, aluminum silicates, phenol-formaldehyde and polystyrene resins, asbestos, and the like; plasticizers and extenders such as dialkyl and diaryl organic acids like diisohutyl, diisooctyl, diisodecyl and dibenzyl oleates, stearates, sebacates, azelates, phthalates, and the like, ASTM type 2 petroleum oils, ASTM D-2226 aromatic, naphthalenic and paraffinic oils, castor oil, tall oil, glycerin, and the like; antioxidants, antiozonants, and stabilizers such as di-B-napthyl-pphenylenediamine, phenyl-B-napthylamine, dioctyl-pphenylenediamine, N-l ,B-dimethylbutyl-N-phenyl-pphenylenediamine, 4-isopropylamino diphenylaminc, 2,6-di-t-butyl paracresol, 2,2'-methylenebis-( 4-ethyl-6- t-butyl phenol), 2,2'-thiobis-(4-methyl-6-t-butyl phenol bispheno|-2,2 '-methylenebis-6-t-butyl-4-ethyl phenol, 4,4'-butylidenebis-(6-t-butyl-m-cresol), 2-(4- hydroxy-3,S-t-butylaniline )-4,6-bis( octylthio l ,3,5- triazine, hexahydro-l ,3,5-tris-B-( 3,5-di-t-butyl-4- hydroxyphenyl )propionyl-s-triazine, tris-( 3,5-di-tbutyl-4-hydroxybenzyl )isocyanurate, tetrakismethylene-3( 3 ,5 '-di-t-butyl-4'-hydroxyphenyl )propionate methane, distearyl thiodipropionate, dilauryl thiodipropionate, tri(nonlatedphenyl) phosphite, and the like; and other ingredients such as pigments, tackifiers, flame retardants, fungicides and the like.

The novel compositions present a unique balancing of the influences of each ingredient, which balance is struck only in the presence of the defined morpholinothioamide compound.

The morpholinothioamides are prepared by reacting N-morpholinosulfenyl chloride with the corresponding oxamide or cyclic hydrocarbon imide. The reactants are employed on about a l to 1 molar ratio, though an excess of either compound, preferably the amide, can be used. A base catalyst such as a tertiary amine like trimethyl amine or tricthyl amine is used. The N- morpholinosulfcnyl chloride is prepared prior to use. it is usually stored as a solution of the compound in carbon tetrachloride, trichloroethylene, or the like (which also serves we a solvent for the reaction). The morpholinosulfenyl chloride must be prepared, stored, and used in the absence of water, as it reacts strongly and even violently, with water.

The oxamide employed has the formula where R is defined as above. The cyclic hydrocarbon imide employed has a labile hydrogen on the imide nitrogen atom; i.e., has a OHO group. Examples of the oxamides and imides are oxamide, diethyloxamide, oxanilide, phthalimide, 2,3- napthalimide, pyrometallitic diimide, and the like.

The amide (or imide) is added to a reactor vessel containing a solvent therefor. Examples of solvents are tetrahydrofuran, dimcthylacetamide, dimethylformamide, and the like. The base catalyst is added, followed by a solution of N-rnorpholinosulfenyl chloride which is added slowly to the reactor mix. The solvent for the amide and the sulfenyl chloride are usually different and may not be miscible in each other. An exothermic reaction occurs upon the addition of the morpholinosulfenyl chloride. Temperature of the reaction ranges from about 10C. to about 60C. External heating or cooling can be employed to control the temperature. Reaction time is from about I to 5 hours. The morpholinothioamide that forms is usually not soluble in the solvcnt(s), and precipitates out as it is formed thereby resulting in a slurry. After reaction, the reactor slurry is cooled down and the product filtered out. The material is dried, and can be purified by washing with water or acetone and/or by recrystallizing the material from ethanol-acetone, chloroform, carbon tetrachlo ride-benzene, or other solvent(s). When the amide (or imide) employed has two or more labile hydrogen atoms on it, the resulting morpholinothioamide can contain more than one morpholinothio group.

The novel vulcanizable rubber compositions described herein were evaluated for their scorch safety and their cured original and aged properties, with particular attention given to stress-strain properties; ie., tensile, modulus, and elongation. Scorch time can be measured using a number of different methods. A standard method is ASTM procedure D-l646, wherein, using a large rotor, A T value is determined at a specific temperature. This value is the time in minutes for a composition, heated at a given temperature, to rise 5 units over a minimum viscosity value. Scorch time can also be determined using a Monsanto Rheometer and measuring T the time in minutes for a heated composition to register to advance of 2 chart units over the minimum value. Another method is to use the B.F.G. Cone Curometer described in US. Pat. No. 3,494,172, and measure T 2 or T,,, 3, the time to rise 2 (or 3) inch-pounds over a minimum torque value. Original tensile, modulus, and elongation were measured following ASTM D-4l2. Hardness was measured following ASTM D676 (Durometer A). Aging was done at 212F. in an oven following ASTM D-573. Hysteresis data was obtained following the procedure ASTM D-623 (B.F.G. Flexometer).

The following Examples serve to more fully illustrate the invention.

EXAMPLE I Preparation of 4-morpholinosulfenyl chloride.

The morpholinosulfenyl chloride must be prepared, stored and used in the absence of water, as it reacts the product washed with ethanol and dried to yield 677 grams of material having a melting point of about 2l0C. The yield, based upon the amount of phthalimide used, was 88% by weight.

strongly and even violently with water. The reaction 5 consists of contacting dithiobismorpholine with chlo- EXAMPLE 1 Preferably in Solution Temperature Of 9 Following the procedure in Example I, a solution of acflon about l0 to about 50 N-morpholinosulfenyl chloride in trichloroethylene obismorpholme, 47.2 grams (0.2 mole) was placed in 10 was prepared f 235 grams 1 m0]@) fN di a reactor vessel containing 400 milliliters of carbon tetthiobismorpholine d 7 3 grams 0 03 mole) f h| rachlfmde- The Solution was Fooled to and ride. The solution, which contained about 0.2 mole of Chlorme gas throl-lgh ll at a of grams the sulfenyl chloride, was slowly added to a solution of p hour for 27 mmutcsz for 11 total of grains 22.8 grams (0.095 mole) of oxanilide and 20.2 grams l' The tesullmg yellow'colored Solullon 15 (0.2 mole) of triethylamine in 230 milliliters of dimethwas Stored for future use ylacetamide. Temperature during the addition rose from room temperature to about 46C. After stirring EXMAPLE ll for L5 hours the resultant slurry was filtered to isolate Preparation of N-( 4-morpholinothio)phthalimidc. produjct' T rg fi F Phthalimide, 55.9 grams (0.38 mole) was placed in g gj ggf f I f g w 9)? fll a reactor vessel containing 500 milliliters of tetrahydroh 0 F l? i fstmg furan. 40.5 grams (0.4 mole) of tricthylamine was ffz .i t f l y i added. The morpholinosulfenyl chloride solution, pret l f e Smd I g 9 morp 01m)- pared in Example I and containing about 0.4 molc'of thlomxdmhde unredctc exam I the compound, was employed. The solution was added E at the rate of l4 milliliters per minute to the reactor so- XAMPLE IV lution. During the addition, the temperature rose to Natural rubber was mixed with various rubber comabout C. A slurry formed. The mix was stirred for pounding ingredients to provide a masterbatch accord- 3 hours at room temperature. The product was isolated ing to the recipe: 100 parts by weight of Natural pale by filtration and dried to yield 68.4 grams of material. crepe rubber, 50 parts HAF carbon black, 5 parts zinc This was dissolved in an ethanol-acetone solution and Oxide, 3 Parts Sieaflc acid, 2 Paris N l im hyl utylprecipitated out by cooling to yield 55.7 grams of a N'-phenyl-p-phenylenediamine. 0.75 part Agerite white solid having a melting point of 212 to 217C. N- Superflex (diphenylamineacetone condensation prod- (4-morpholinothio)phthalimide having the formula uct), and 0.25 part N,N'-diphenyl-p- C H, N- ,O S has 54.5% by weight of carbon, 4.6% by phenylenediamine. The masterbatch was mixed in a drogen, I067: nitrogen, and I2. 1% by weight of sulfur. Banbury mixer following a standard mixing procedure. The values found were 54,87 carbon 46% hydrogen, Portions Of th masterbatch were put on a IWO-l'Oll mill, l0.7'/( nitrogen, and 12.0% by weight of sulfur. and curative ingredients were added. The following Following the procedure given above, 3.04 moles of 40 recipes were evaluated (in parts by weight) Masterhateh l6l 101 101 lol lol BMD' 3.0 OBTS 3.0 3.0 3.0 3.0 MBT" 0. 025 0.3a MTP' 2.240 2.80 2.80 2.240 Sulfur 0.50 0.50 0.50 0.50 0.50 BFG Cone Curometer data applied pressure in.-lbs./min. 3 I 2 3 3 Atorque. inch-pounds 88 [07 l l l 79 H0 T,.2, minutes 4.4 10.8 l0.5 7.4 6.6 Percent increase in scorch sal'et I46 U8 68 Cured minutes at 284F.

3000i modulus, psi 2280 230) 2390 22l0 2210 Tensile psi 3930 3690 3820 4080 3990 Elongation. percent 400 430 440 500 490 6 days at 2l2F.

300W modulus, psi 2670 2490 2500 Tensile, psi 2740 2500 2800 2800 3000 Elongation. percent 3) fill) 320 340 350 Percent decrease in tensile 30 32 27 3] 25 'Z-lvenlothialyl 4-mnrph1llin0 disullide "bl-ox dieth)lel\cJ-hen/olhinlyl .slllll'lizilnide "Z-niercaptuhen/rithituule J-nitvr hrilinothiophthalimide from Example ll "to wage of two samples Sample 1 is a control sample. It demonstrates the 5 short scorch time and excellent original and thermal aged properties that are obtained using a BMD-sulfur cure system. Samples 2 to 5 are novel compositions of this invention. The samples show a unique combination of improved scorch safety and excellent original and aged properties. The retention of tensile strength after aging is as good as or better than that of Sample 'l the control, while at least a 50% increase in scorch safety as the known cure system of BMD-sulfur (Sample 1 The excellent original and aged properties are obtained along with an increase in scorch safety. Samples 3 to 6 show the use of a thiuram accelerator as an optional is obtained. Samples 3 to show that the use of small 5 fifth ingredient in the compositions. levels of a 2-thiobenzothiazole accelerator yields somewhat higher original and aged tensile properties.

EXAMPLE V A masterbatch was prepared containing 70 parts by weight of natural rubber, parts of cis-polyisoprene rubber. 50 parts of HAF carbon black, 5 parts of zinc EXAMPLE VI The masterbatch prepared in Example V was also l0 used in an evaluation of a novel cure system using the N,N'-bis(4-morpholinothio)oxanilide prepared in Example lll. The recipes used are as follows:

Masterhateh lbl lfil Ifil lol BMD 3 25 OBTS 3.0 2.83 2.88 MBT 0.15 025 MBTS' 0.15 BMTO" 2.30 2.73 2.73 Sulfur 0.5 0,5 0,5 0.5 BFG (one C'umrneter applied pressure.

in-lbs/min. 3 3 3 3 Atorque. inch-pounds 101 89 87 93 T,..' minutes 7.3 10.8 17.4 20.7 Percent increase in scorch safety 48 L38 I84 Cured 75 minutes at Iii-PF.

300W modulus. psi 2470 2420 2470 2490 Tensile. psi 3780 3550 3360 3390 Elongation. percent 410 400 380 390 Aged 7 days at 2l2F.

300% modulus. psi 2580 Tensile. psi 2600 2690 2420 2270 Elongation. percent 280 3l0 270 260 Percent decrease in tensile 3| 24 28 33 Percent decrease in elongation 32 23 29 33 oxide, 3.0 pans of stearic acid, 2.0 parts of N-l,3- dimethylbutyl-N-phenyl-p-phenylenediamine, and l .0 part of Agerite Superflex (diphenylamine-acetone con- Samples 2 to 4 are novel compositions of this invention. The data shows that these compositions yield as good as or better aging properties with at least about a densation product). The masterbatch was used in an increase in scorch safety compared to the known evaluation of various cure systems. The recipes used and data obtained are as follows:

BMD-sulfur cure system (Sample I).

The use of the BMD-sulfur cure system yields vulcan- Mustcrhatch lfil lfil lftl lfil lfil lfil BMD 3.0 OBTS 3.0 2.0 2.25 2.25 [.50 MBT 0.25 TMTM. 0.25 (1.38 0.25 0.3 MTP 2.80 2,00 1.50 l 50 1.50 Sulfur 0.5 0.5 0.65 0.5 0.8 0,8 BFG Cone Curometer applied pressure.

in-lbs/min. 3 3 4 4 3 3 Atorque. inch-pounds 7] 89 I I3 72 i0) I03 T,,.2. minutes 6.6 l L0 9.0 13.4 9.8 9.2 Percent increase in scorch safety 67 36 103 49 39 Cured 75 minutes at 284F.

300V: modulus. psi 2230 2280 2570 2310 2690 2660 Tensile. psi 3950 3350 40l0 3590 3440 36l0 Elongation. percent 460 400 430 420 360 380 Aged 7 days at 212F.

300% modulus. psi 2bl0 26l0 2520 Tensile. psi 26(10 2680 2830 2720 2230 2570 Elongation. percent 300 fill) 320 320 240 290 Percent decrease in tensile 33 20 29 24 35 29 Percent decrease in elongation 35 23 2h 24 33 24 'tetmrnethylthiuram monosult'ide "aneruge of (no samples izates having excellent original and thermal aged properties. especially tensile, modulus, and elongation. Such vulcanizates would be particularly useful as hose,

The example demonstrates that the novel cure systems and compositions of this invention (Samples 2 to 6) exhibit as good as or better thermal aged properties molded gaskets, tires and the like which are subject to heat during their use. The BMD-sulfur cure system is limited in its use by its relatively short scorch time. The use of known cure retarders and vulcanization inhibitors does not provide for significantly increased scorch times. For example, Santogard PVI (N-cyclohexylthiophthalimide) a commercial cure retarder, was used at l .0 part per 100 parts of rubber in the masterbatch recipe given in Example l\/. 3 parts of BMD and part of sulfur was used as the cure system. BFG Cone Curometer data was obtained at 284F. T, 2 of the recipe without the Santogard PVI present was 3.9 minutes. With 1.0 part of PVI present, the T,,, 2 value was 4.8 minutes, an increase in scorch safety of only 23%. At no time, in the experiments run. did the PV] increase scorch safety over 50% of the control value. In contrast, many times the novel cure systems of this invention increased scorch safety, at no loss in aging characteristics, over 50% and up to about 200%.

Following the procedures given in Examples I, ll and Ill, orther morpholinothioamide compounds were prepared. Morpholinosulfenyl chloride was reacted with Z-imidazolidinone to prepare both l,3-bis(4- morpholinothio)-2-imidazolidinone and the monosubstituted compound. Other compounds prepared N-(4 were N-( 4-morpholinothio )succinimide, morpholinothio )-0-benzoic sulfimide, N-( 4- morpholinothio )hydantoin, and N,N'-bis( 4- morpholinothio)hydantoin, All six of the compounds were evaluated for their utility in the compositions disclosed in this application. None of these compounds yielded a composition having both the increased scorch safety and the excellent original and aged properties of the claimed compositions. This illustrates the unique features of the claimed morpholinothiooxamides and morpholinothio cyclic imides.

l claim:

I. A vulcanizable composition comprising l a sulfur vulcanizable rubber having an olefinic unsaturation content of from about 0.5 percent to about 50 percent by weight of the rubber, (2) sulfur, (3) a thiazole sulfenamide accelerator of the formula T-S-A, wherein T is a thiazole ring group and A is selected from the group consisting of an alkyl radical containing l to 4 carbon atoms, and (4) a morpholinothiooxamide of the formula R.. WN/ N mium,. and

wherein R is selected from the group consisting of hydrogen, alkyl radicals containing 1 to 24 carbon atoms, an aryl, alkaryl, or aralkyl radical containing 6 to 18 carbon atoms, a cycloalkyl radical containing 3 to 8 carbon atoms in the ring, and the group 2. A composition of claim 1 wherein the sulfur vulcanizable rubber is selected from the group consisting of natural rubber, cis-polyisoprene, cis-polybutadiene, emulsion polybutadiene, butadiene-acrylonitrile rubber, isoprene-acrylonitrile rubber, polychloroprene, polypentenamer polymer, butadiene-styrene rubber, isoprene-styrene rubber, isoprene-isobutylene rubber, and ethylene-propylene-diene polymers.

3. A composition of claim I containing as an ingredient a Z-thiobenzothiazole of the formula where X is selected from the group consisting of hydrogen, an alkyl radical containing l to l8 carbon atoms, an aryl radical, a benzothiazolethio group, and a monoor divalent radical selected from the group consisting of ammonium, sodium, potassium, calcium, zinc, cadmium, copper, and lead.

4. A composition of claim 1 containing as an ingredient, a thiuram of the formula where A is defined as before, B is defined as A, and z is l or 2.

5. A composition of claim 2 wherein a morpholino thiooxamide of the formula is used: where R is a phenyl radical and R, is hydrogen, an alkyl radical containing 1 to about l2 carbon atoms, a phenyl radical, a cyclohexyl radical, or a group.

fenamide accelerator is N-oxydiethylene-Z- benzothiazyl sulfenamide, the morpholinothiooxamide is N.N-bis(4-m0rpholinothio) oxanilide, and containing as an ingredient 2,2-ben2othiuzyl disulfidc. 

1. A VULCANIZABLE COMPOSITION COMPRISING (1) A SULFUR VULCANIZABLE RUBBER HAVING AN OLEFINIC UNSATURATION CONTENT OF FROM ABOUT 0.5 PERCENT TO ABOUT 50 PERCENT BY WEIGHT OF THE RUBBER, (2) SULFUR, (3) A THIAZOLE SULFENAMIDE ACCELERATOR OF THE FORMULA T-S-A, WHEREIN T IS A THIAZOLE RING GROUP AND A IS SELECTED FROM THE GROUP CONSISTING OF
 2. A composition of claim 1 wherein the sulfur vulcanizable rubber is selected from the group consisting of natural rubber, cis-polyisoprene, cis-polybutadiene, emulsion polybutadiene, butadiene-acrylonitrile rubber, isoprene-acrylonitrile rubber, polychloroprene, polypentenamer polymer, butadiene-styrene rubber, isoprene-styrene rubber, isoprene-isobutylene rubber, and ethylene-propylene-diene polymers.
 3. A composition of claim 1 containing as an ingredient a 2-thiobenzothiazole of the formula
 4. A composition of claim 1 containing as an ingredient, a thiuram of the formula
 5. A composition of claim 2 wherein a morpholinothiooxamide of the formula
 6. A composition of claim 5 wherein the thiazole sulfenamide accelerator is N-oxydiethylene-2-benzothiazyl sulfenamide, the morpholinothiooxamide is N,N''-bis(4-morpholinothio)oxanilide, and containing as an ingredient, 2-mercaptobenzothiazole.
 7. A composition of claim 5 wherein the thiazole sulfenamide accelerator is N-oxydiethylene-2-benzothiazyl sulfenamide, the morpholinothiooxamide is N,N-bis(4-morpholinothio) oxanilide, and containing as an ingredient 2,2''-benzothiazyl disulfide. 